1. Uses of Herbicides
An herbicide is a compound which controls or modifies plant growth, e.g., killing, retarding, defoliating, desiccating, regulating, stunting, tillering, stimulating, and dwarfing. "Plant" refers to all physical parts, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage, and fruits. "Plant growth" is meant to include all phases of development from seed germination to natural or induced cessation of life.
Herbicides are generally used to control or eradicate weed pests. They have gained a high degree of commercial success because it has been shown that such control can increase crop yield and reduce harvesting costs.
Herbicidal effectiveness is dependent upon several variables. One of these is the time or growth related method of application. The most popular methods of application include: pre-plant incorporation into the soil; pre-emergence surface treatment of seeded soil; and post-emergence treatment of the plant and soil.
The most important determinant of herbicidal effectiveness is the susceptibility of the target weed. Certain herbicidal compounds are phytotoxic to some weed species but not to others.
The manufacturer of the herbicide recommends a range of rates and concentrations calculated to maximize weed control. The range of rates varies from approximately 0.01 to 50 pounds per acre (0.0112 to 56 kilograms per hectare (k/ha)), usually from 0.1 to 25 pounds per acre (0.112 to 28 k/ha). The actual amount used depends upon several considerations, including particular weed susceptibility and overall cost limitations.
2. Need for Herbicidal Antidotes
Unfortunately, few herbicides are selective exclusively of weed species. Many are toxic to both weeds and the intended crop beneficiary. Therefore, a particular herbicide's use may be proscribed by its injurious effect on the cultivated crop even though it may otherwise provide excellent control of weeds plaguing that crop.
To preserve the beneficial aspects of herbicide use and to mitigate crop damage, many herbicidal antidotes have been prepared. These antidotes reduce or eliminate damage to the crop without substantially impairing the ameliorative effect of the herbicide. See U.S. Pat. Nos. 4,021,224 and 4,021,229 and Belgian Pat. No. 846,894.
Although several explanatory theories have been advanced, the precise mechanism by which an antidote reduces herbicidal crop injury while retaining weed injury has not been conclusively established. An antidote compound may in fact be a remedy, interferent, protectant, or antagonist. As used herein, "antidote" describes the effect of establishing herbicidal selectivity.
Thiocarbamate herbicides are particularly effective in the control of grassy type weeds which interfere with the cultivation of a wide variety of crops, e.g., barley, corn, lentils, peanuts, peas, potatoes, soybeans, spinach, tobacco and tomatoes. Frequently, their beneficial use requires the addition of an antidotal compound.